GABITOV, D. I.; GIBNEY, J. The dynamics of the elastic pendulum. p. 10, [s.d.].
Dynamics of the Elastic Pendulum Qisong Xiao; Shenghao Xia ; Corey Zammit; Nirantha Balagopal; Zijun Li
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MIT Porfessor Walter Lewin's lecture about Simple Harmonic Motion, Period of a Pendulum, Period of a mass-spring system, and Hooke's Law https://www.valenciavikings.com/apps/video/watch.jsp?v=134709